From: Kevin Coffman Date: Thu, 8 Feb 2007 22:27:19 +0000 (-0500) Subject: Stop using storage after free X-Git-Tag: nfs-utils-1-0-11~12 X-Git-Url: https://git.decadent.org.uk/gitweb/?p=nfs-utils.git;a=commitdiff_plain;h=4a2e207f73f9ebe938e882f9419a2716fe751481;hp=e54fb292fcd9253743fc17ba0af26dcbb0723a5d Stop using storage after free Signed-off-by: Jeff Layton Signed-off-by: Kevin Coffman The previous patch seems to expose a use after free bug in dirscancb. At least, I could reliably reproduce a segfault by doing a bunch of mounts and then unmounting them all. The code uses the following list macro: TAILQ_FOREACH(ic, icq, ic_next) { ...to iterate over all of the ic entries and clean up any that no longer have a corresponding directory in rpc_pipefs. This macro unrolls into: for(ic=icq->tqh_first; ic != NULL; ic=ic->ic_next.tqe_next) { ...but within this loop, we can free ic, and then the for loop can trip over that when it tries to do the iteration. The attached patch works around this by not using the TAILQ_FOREACH macro and saving off the tqe_next pointer prior to the free. Again, this was tested on a patched 1.0.6, but the 1.0.10 code is very similar, and I think the problem exists there as well. Signed-off-by: Neil Brown --- diff --git a/utils/idmapd/idmapd.c b/utils/idmapd/idmapd.c index cbb0b6a..b30b69e 100644 --- a/utils/idmapd/idmapd.c +++ b/utils/idmapd/idmapd.c @@ -444,7 +444,7 @@ dirscancb(int fd, short which, void *data) { int nent, i; struct dirent **ents; - struct idmap_client *ic; + struct idmap_client *ic, *nextic; char path[PATH_MAX]; struct idmap_clientq *icq = data; @@ -498,7 +498,9 @@ dirscancb(int fd, short which, void *data) } } - TAILQ_FOREACH(ic, icq, ic_next) { + ic = TAILQ_FIRST(icq); + while(ic != NULL) { + nextic=TAILQ_NEXT(ic, ic_next); if (!ic->ic_scanned) { event_del(&ic->ic_event); close(ic->ic_fd); @@ -511,6 +513,7 @@ dirscancb(int fd, short which, void *data) free(ic); } else ic->ic_scanned = 0; + ic = nextic; } out: